1. Technical Field
The inventions disclosed herein generally relate to a composition used for the fueling and re-fueling of electrochemical devices.
2. Related Art
A fuel cell is a device that converts chemical energy directly into electrical energy. They typically operate with higher efficiencies than traditional combustion engines. In addition, emission of greenhouse gasses from fuel cells is reduced or eliminated. The prospect of affordable, clean fuel for stationary and transportation applications are several of the driving forces behind the Hydrogen Economy, where the energy infrastructure is based on hydrogen instead of oil. Liquid hydrocarbon fuels, such as methanol, are also advantageous in fuel cells. Fuel cell electrodes and devices have been previously described in U.S. Ser. No. 60/896,722. The disclosure of this application is incorporated herein by reference.
Devices that are configured to electrochemically convert reactants, for example water, into products such as hydrogen and oxygen when energy is applied are generally known as electrolyzers. For an electrolyzer to operate with high efficiency, the amount of product produced during reaction should be maximized relative to the amount of energy input. In many conventional devices, low catalyst utilization in the electrodes, cell resistance, inefficient movement of electrolyte, and inefficient collection of reaction products from the electrolyte stream contribute to significant efficiency loss. In many cases, low efficiency is compensated for by operating the cell at a low rate (current). This strategy does increase efficiency; however, it also lowers the amount of products that can be produced at a given time. The electrolyzer described in the preferred embodiments can operate both at high rates and efficiencies. Electrolysis electrodes and devices have been previously described in U.S. Ser. No. 11/716,375. The disclosure of this application is incorporated herein by reference.
Platinum is highly catalytic for hydrogen or hydrocarbon oxidation and oxygen reduction in gas diffusion electrodes for a variety of fuel cells, or splitting of reagents such as water in electrolysis cells. However, this noble metal is a rapidly depleting non-renewable resource and is consequently expensive. Current price for bulk platinum black is $75.00/gram. The associated cost of a platinum deposited electrode, typically loaded anywhere from 2-8 mg/cm2, is widely considered to be a hurdle to widespread commercialization. With the gaining demand for alternative energy sources by consumers, efficient catalysts, new fuel cell electrodes and designs must be discovered to alleviate the demand and expense of platinum. Based on this, considerable effort is being dedicated to find an alternative catalyst which can match or exceed platinum's electrical performance. Method of synthesis of metal nanoparticles has been previously described in U.S. Ser. No. 10/840,409, as well as their use in air cathodes for batteries in U.S. Ser. No. 10/983,993.
A fluidized bed reactor (FBR) is designed to carry out chemical reactions that take place between materials solids, and liquids and/or gasses. In this type of reactor, a gas or liquid is passed through catalyst particles such that the catalyst particles are supported by an upflow of gas. The gas should have a significant enough velocity such that the catalyst particles remain suspended. The FBR is widely used in the chemical industry because of excellent heat and mass transfer characteristics. However, the use of FBRs is relatively unexplored in conjunction with electrochemical cells, and has not been previously demonstrated with catalyst nanoparticles. Because the catalyst particles can be suspended in a liquid electrolyte, it is possible to re-fuel the electrochemical FBR when the electrolyte is depleted or the catalyst becomes inactive.